1. Field of the Invention
The present invention relates to a wiring structure for a semiconductor device that is mounted to a substrate. More particularly, the present invention relates to a wiring structure for a semiconductor device for electric power applications.
2. Background Information
Japanese Laid-Open Patent Publication No. 2003-164040 discloses one of the conventional wiring structures for a semiconductor device. For example, in such a conventional wiring structure, a power device comprising a semiconductor chip is mounted to a substrate to form a module. A semiconductor chip constituting a power device is mounted to a metal substrate constituting a mounting substrate. An insulating layer is disposed between the semiconductor chip and the metal substrate. The metal substrate is, for example, a copper plate having a thickness of approximately 4 millimeters. The insulating layer is, for example, made of ceramic and connected to the metal substrate with solder.
An anode wiring (a collector wiring in this example) made of copper foil is formed such that the anode wiring adheres closely to the insulating layer. The semiconductor chip has a collector electrode on its rear surface and the anode wiring and the collector electrode of the semiconductor chip are connected and fixedly coupled together with solder. Similarly to the anode wiring, a copper foil cathode wiring (an emitter wiring in this example) is also formed such that the cathode wiring adheres closely to the insulating layer. The cathode wiring is electrically connected to an emitter pad formed on the semiconductor chip by an aluminum wire.
Main electrodes of the module are made of copper plates having a thickness of approximately 1 millimeter. The main electrode is connected to the anode wiring and the main electrode is connected to the cathode wiring. One end of each of the main electrodes is exposed to the outside of a plastic external shell of the module and has a screw hole provided therein. The screw holes of the main electrodes enable the main electrodes and to be connected to an external bus bar with screws.
In the conventional wiring structure explained above, the main wirings connected to the semiconductor device, i.e., the anode wiring and the cathode wiring, are separated by a distance. Consequently, there are cases in which the wiring inductance becomes large and the induced voltage restricts the drive conditions of the peripheral drive circuitry when the semiconductor chip executes high-speed switching operations. Moreover, each time a switching operation is executed in the conventional wiring structure explained above, electromagnetic waves are emitted from the main wirings and cause electromagnetic interference (EMI) in the peripheral drive circuitry. The possibility of this problem occurring is particularly high in small power supply units and IPMs (intelligent power modules) in which a drive circuit is provided integrally inside a module such as in the conventional wiring structure in order to achieve a compact wiring structure. Typically a shielding plate is provided in the vicinity of the drive circuit in order to avoid such interference, but this is not a fundamental solution to the problem.
In another example of a conventional wiring structure with a semiconductor chip mounted to a substrate, an anode wiring and a cathode wiring having a sheet-shape and approximately the same width are mounted to a metal substrate through an insulating layer. A semiconductor chip is mounted between the anode wiring and the cathode wiring such that a cathode electrode formed on the semiconductor chip with solder bumps is connected to the cathode wiring.
The anode wiring is connected to an anode wiring formed on the insulating layer and the cathode wiring is connected to a cathode wiring formed on the insulating layer. A control signal electrode formed on the semiconductor chip is connected to a control signal wiring pattern formed on the insulating layer through another control signal wiring pattern. The semiconductor chip is packaged in such a manner as to be enclosed inside the module external shell.
In this type of conventional wiring structure, the main electrodes, i.e., the anode wiring and the cathode wiring, are formed to extend in opposite directions with respect to the module. As a result, the distance between the anode wiring and the cathode wiring on the metal substrate is large and acts as a source of electromagnetic interference similarly to the situation depicted in the conventional wiring structure.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved semiconductor device wiring structure that reduces the wiring inductance and suppresses the generation of interfering electromagnetic waves. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.